There are conventionally known systems that obtain data such as temperature setting data, power consumption data, and operating mode data from air conditioners and the like when monitoring air conditioners. The monitoring system described in Japanese Laid-Open Patent Publication No. 2004-226062 given below is an example of a system for monitoring abnormal data produced by air conditioners. In this monitoring system, when an abnormality occurs in the air conditioner, details of the abnormality, including data on the occurrence of the abnormality and data on the most recent operating status, are transmitted from a monitoring device that is monitoring the air conditioner to a remote monitoring device. The details on the abnormality that have been transmitted are then stored and collected as needed in the database for the operating data in the remote monitoring device. Onsite service staff members can thereby promptly handle abnormal occurrences by communicating over the internet using a portable terminal in their personal possession to extract and receive data on the operating status from the last 30 minutes to the present from among the details of the abnormality in the database for the operating data. That is, in the process carried out by this monitoring system, data on the operating status within a certain recent time range is extracted from the data that has been collected in the database for the operating data.